A federal grand jury indicted Hunter and his wife Margaret in August over allegations of improperly using campaign funds between 2009 and 2016 for personal expenses, such as vacations and dental bills. In spite of the indictment, Hunter maintained a polling lead over Campa-Najjar, a small business owner, for most of September and October.

The 50th Congressional District includes parts of Riverside County and San Diego County, including San Marcos and Escondido.

Despite his win, Hunter's lead dwindled from 15 percentage points in a late September poll from Monmouth University to just three points in an Oct. 25-29 poll from SurveyUSA.

Hunter's campaign released a much-debated TV ad in September that framed Campa-Najjar as a terrorist sympathizer and claimed he is supported by the fundamentalist Sunni Islamic extremist group the Muslim Brotherhood. The ad also called Campa-Najjar a security risk, despite the fact he served as a White House staffer during the Obama administration.

There are currently 139,636 registered Republicans in the 50th district compared to 94,699 registered Democrats, according to the Registrar of Voters.

Hunter, a former U.S. Marine and son of former Rep. Duncan Lee Hunter, has served in Congress since 2009. Hunter first represented District 52, but redistricting after the 2010 census shifted him to the 50th district.